Second critical endpoint in the peridotite-H2O system

Kenji Mibe, Masami Kanzaki, Tatsushiko Kawamoto, Kyoko N. Matsukage, Yingwei Fei, Shigeaki Ono


102 被引用数 (Scopus)


The second critical endpoint in the peridotite-H2O system has been determied using an X-ray radiography technique together with a Kawai-type, double-stage, multianvil system driven by DIA-type cubic press (SPEED-1500) installed at SPring-8, Japan. The pressure of the second critical endpoint was determined by the appearance and disappearance of round shape in the radiographic images with changing the experimental pressure. In the experiments up to 3.6 GPa, two fluid phases (i.e., aqueous fluid and hydrous silicate melt) were observed. At 4.0 GPa, however, we could not distinguish these two phases in the radiographic images. These observations indicate the second critical endpoint occurs at around 3.8 GPa and 1000°C (corresponding to a depth of ∼110 km) in the peridotite-H2O system. Our experimental results suggest that hydrous silicate melt and aqueous fluid in the Earth's mantle become indistinguishable from each other and that melting temperature of hydrous mantle peridotite can no longer be defined beyond this critical condition. This position of the second critical endpoint could explain the previously observed drastic changes in composition and connectivity of aqueous fluid in mantle peridotite at around 3-4 GPa and could play an important role in magmatism and chemical evolution of the Earth's interior.

ジャーナルJournal of Geophysical Research: Solid Earth
出版ステータスPublished - 3月 4 2007

ASJC Scopus subject areas

  • 地球物理学
  • 地球化学および岩石学
  • 地球惑星科学(その他)
  • 宇宙惑星科学


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